Hydrogenated derivatives of 7-cyano-2, 5-heptadienoic acid and its esters



' 2,968,466 HYDROGENATED DERIVATIVES F 7-CYANO-2,5-

HEPTADIENOIC ACID AND rrs, ESTERS Gian Paolo Chiusoli, Milan, Italy, assignor to Montecafini SocietaGenerale per lIndustria Mineraria e Chimica, a

corporation of Italy e No Drawing. Filed 0ct. 7, 1958, Ser. No. 765,734 Claims priority, application Italy Oct. 10, 1957 14 Claims. -(Cl. 260-404) 2,978,466 Patented Apr. 4, 1961,

The hydrogenation of the acid or its esters to obtain omega-aminoc'aprylic acid and its esters can be'carried out either on the distillate or on the raw product.

.If Raneynickel is used, the reaction is preferably car ried out at between 20 and 100, under a hydrogen pressure up to 200 atm., in the presence of ammonia in The present invention relates to the obtainment ofhyorder to decrease the tendency to the formation of secondary amine.

The final product obtained by hydrogenation can be distilled if it is an ester. It should however be noted that it is difiicult in this way to avoid a partial po-lycondensation of the aminoester, especially so if the latter is a lower ester. In such case, it is convenient to saponify the product by boiling it with amineral acid, such as hydrochloric or sulfuric acid, and then to neutralize it with ammonia, dry it, and carefully extract the aminoacid with absolute alcohol.

The aminoacid can also be purified through its hydrochloride (melting point 145-146 C.).

In order to obtain a highly pure product it is better the ' to hydrogenate the seminitrile in two stages. Palladium obtaining omega-amino c'aprylic acid is the Be'ckmann 'rearrangement of 9-keto stearic acid oxime, followed by decomposition of the product with concentrated hydrochloric acid at 180 C. I

Under these conditions only a small amount of aminoacid is formed, the remaining portion consisting prevailingly nonylamine, decanoic acid and azelaicacid. By the process described herein, omega-aminocaprylic acid can be obtained in a most simple way. Moreover, the esters of lower alcohols also become available,,Which can be distilled and polymerized as such Without saponitying them and separating the aminoacid.

For a limit of practical convenience, the loweralcohols here'claimed are aliphatic alcohols having 1 to 4 carbon atoms. i

The hydrogenation leads to omega-aminocaprylic acid and esters thereof, the reaction being as follows:

RO0CCH=CHOH:CH=OHCH;CN i

- Ro'oo-(onm-Nn'.

The selective hydrogenation of the double bonds makes it possible to obtain the. seminitrile of suberic acid and ithe'esters thereof, from .which, by saponification, suberic acid can easily be obtained. This reaction scheme is as nooo-wnm-ooon Bysaponificatio n of the starting product with concentrated hydrochloric acid, 2,4-octadiendioic acid is obtained. The displacement of the double bond to the conjugated position takes place, as can be readily observed irom the ultraviolet spectra (absorption maximum at 2540 A.). From this product, by hydrogenation, suberic acid is again obtained, as follows:

' RCQO-CH=CH-CH,CH=CHCHCN,

. H01 R0oo-oH=on oH=on-cH.-om-o0011 nooc onz)looon is a very suitable catalyst for the selective hydrogenation of the double bonds and can be used even in very low amounts when supported on carriers. The hydrogenation is very rapid and takes place at low temperature, preferably at between 10 and C. under a hydrogen pressure. The successive stage of hydrogenation of the nitrile to the amino-group is carried out, after removal of. the palladium catalyst by .filtration, on a nickechromium catalyst at between 20 and 60 C.

The hydrogenation in two stages also oliers other The distillation of the raw product ob tained from the reaction with acetylene and carbon monoxide can be avoided. It is possible, instead, to distill possibilities.

the product when already hydrogenated at the double bonds, that is the suberic seminitrile and its esters- A further advantage ofiered by this process, in addition to the distillation of a more stable product, is the possibility of recovering at the same time a small amount of sebacic dinitrile obtained by hydrogenation of dicyano-octadiene, a secondary product contained in the.

raw product.

Moreover, by starting from a distilled product for the second. hydrogenation stage, the formation of impurities is reduced to a minimum.

From the suberic seminitrile, which is a liquid with a boiling point of 138-142" C. (.10 mm. Hg), andwhich is obtained, as stated above, by selective hydrogenation of the double bond, suberic acid is easily obtained accord ing to known methods.-

Suberic acid can also be obtained by direct saponifica- 7 tion of the octadiendioic seminitrile. By operating with concentrated hydrochloric acid there is obtained the formation of a solid, which precipitates from the hydrochloric solution. This solid consists of 2,4-ootadiendioic acid, being formed by isomerization of 2,5-octadiendioic acid.

This acid, already described in the literature, melts at 221 and has an ultraviolet spectrum with an absorption Example 1 20 g. methyl ester of 7-cyano-2,S-heptadienoic-l acid are dissolved in methanol and after addition of- 10 g. ammonia, are hydrogenated on 5 g. of Raney nickel in an autoclave. i

The hydrogenation takes place readily at 50 The nickel is filtered off, alcohol is removed under vacuum,

Example 2 14 g. of the methyl ester of 7-cyano-2,5-heptadienoic-lacid are hydrogenated for 30 minutes at 30 in methanol solution under a hydrogen pressure of 30 atm. in the presence of 1 g. of catalyst, determined on the basis of supported palladium.

The palladium catalyst is filtered off and g. of a catalyst on the basis of nickel-chromium and 0.3 g. NaOH are added. The hydrogenation is then continued for 30 minutes at 30 under a hydrogen pressure of 30 atm. The nickel is filtered off. The solution appears clear and colorless. Alcohol is distilled off and the solution is refluxed with 36% hydrochloric acid for 3 hours. It is then neutralized with sodium carbonate while heating and about 0.5 g. of a basic oil is extracted with ether.

The solution is then acidified With sulfuric acid, neutralized with ammonia, and dried. The residue is repeatedly extracted with absolute alcohol, eliminating the salt by filtration. The alcohol extract is dried, thus obtaining omega-aminocaprylic.

The hydrochloride of the acid melts at 145146 C.

Example 3 50 g. of the raw product resulting from the reaction l-ch1oro-4-cyanobutene-2 with acetylene, CO, nickel carbonyl and methyl alcohol, are hydrogenated in methyl alcohol with 2 g. palladium catalyst.

The product distilled at 150-160 (18 mm. Hg) yields 45 g. of methyl ester of suberic seminitrile; 3 g. sebacic dinitrile are contained in the distillation residue.

Analysis.--Found: C, 64.04; H, 9.35; N, 7.96. Calculated for C H NO C, 63.88; H, 8.94; N, 8.28.

By hydrogenation of suberic dinitrile and by a treatment similar to that of the preceding example, 33g. omegaaminocaprylic acid are obtained.

Example 4 g. 7-cyano.-2,5 heptadienoic-lacid are neutralized with sodium bicarbonate and hydrogenated in an aqueous ethanol solution first on palladium and then with nickel chromium.

The solution is filtered, saponified with sulfuric acid, neutralized with ammonia and dried. The dry residue is extracted with alcohol disclosed above. 8 g. omegaamino-caprylic acid arethus obtained.

Example 5 Example 6 In a flask equipped with stirrer, reflux condenser, thermometer, gas inlet pipe and separatory funnels, 100 cc. acetone and 10cc. water are placed. The temperature "4 is raised to 40 C. and a stream of 6 liters/h. acetylene and 6 liters/h. carbon monoxide is passed in. Simultaneously 20 g. 1-chloro-4-cyano-butene-2, and 11 cc. nickel carbonyl are introduced over a period of three hours. The solution becomes brown and nickel chloride is separated.

Acetone is distilled off, the residue is taken up again with water and the oil thus formed is separated; 13 g. 7-cyano-2, S-heptadienoic acid are extracted with sodium bicarbonate and then freed by treatment with sulfuric acid.

Example 7 300 cc. acetone and 300 cc. water are introduced into the reaction tube. CO and C H are passed through as in the preceding example. Two acetone solutions, one containing 40 g. chloro-cyanobutene and the other 7 cc. nickel carbonyl, are then introduced. Finally, the gas is discharged and the apparatus is washed with nitrogen. The reaction is carried out as in the preceding example. When the reaction is completed acetone is distilled, the product is separated from nickel chloride and treated with sodium carbonate, thus extracting the acid portion which is then freed by acidification with sulfuric acid and is mixed with ether.

The acid portion, containing 7-cyano-2,5-heptadienoic acid amounts to 34 g. The acidimetric equivalent is 165.

I claim:

1. Process for preparing a compound of the group consisting of omega-amino caprylic acid and its alkanol esters, the alkanol having from 1 to 4 carbon atoms, comprising treating a compound of the group consisting of 7-cyano-2,5-heptadienoic-1 acid and the corresponding alkanol esters thereof with hydrogen in the presence of a nickel hydrogenation catalyst.

2. The process of claim 1 in which the catalyst is Raney nickel catalyst, the process being carried out at 20 to 100 C. in the presence of ammonia, at a hydrogen pressure up to 200 atmospheres.

.3. Process for preparing a compound of the group consisting of omega-amino caprylic acid and its alkanol esters, the alkanol having from 1 to 4 carbon atoms, comprising treating a compound of the group consisting of 7-cyano-2,S-heptadienoic-l acid and the corresponding alkanol esters thereof with hydrogen in the presence of palladium catalyst at between 10 and C., to hydrogenate the heptadienoic double bonds in a first step, removing the palladium, and further carrying out said treatment in a second step at between 20 and 60 C. in the presence of nickel-chromium catalyst, to hydrogenate the cyano radical.

4. A process for preparing an ester of omega-aminocaprylic acid, comprising treating an ester of 7-cyano- 2,5-heptadienoic-1 acid with hydrogen in the presence of a nickel hydrogenation catalyst.

5. A process for preparing an ester of omega-aminocaprylic acid comprising treating an ester of 7-cyano-2,5- heptadienoic-l acid with hydrogen in the presence of a nickel catalyst.

*6. A process for preparing an ester of omega-aminocaprylic acid comprising treating an ester of 7-cyano-2,5-

heptadienoic-l acid with hydrogen in the presence of a Raney nickel catalyst at about 20 to C. in the presence of ammonia, at a hydrogen pressure up to 200 atmospheres.

7. A process for preparing an ester of omega-aminocaprylic acid comprising treating an ester of 7-cyano-2,5- heptadienoic-l acid with hydrogen in the presence of a Raney nickel catalyst at about 20 to 100 C., in the presence of ammonia, at a hydrogen pressure up to 200 atmospheres, the ester being the ester of an alkanol having from 1 to 4 carbon atoms.

8. A process of preparing an alkanol ester of omegaaminocaprylic acid, comprising treating an alkanol ester of 7-cyano-2,5-heptadienoic-l acid with hydrogen under -11. A process for preparing omega-aminocaprylic acid comprising treating 7-cyano-2,5-heptadienoic-1 acid with hydrogen in the presence of a Raney nickel catalyst.

12. A process for preparing omega-aminocaprylic acid comprising treating 7-cyano-2,S-heptadienoiul acid with hydrogen in the presence of a Raney nickel catalyst at about 20 to 100 C., in the presence of ammonia, at a hydrogen pressure up to 200 atmospheres.

13. The process of claim 1 carried out on the raw mixture containing said 7-cyano-2,5-heptadien0ic-l acid, ob tained by reacting 1-ch1oro-4-cyano-butene-2 with acetylene, carbon monoxide and nickel carbonyl.

a 14. Process for preparing a compound of the group consisting of omega-amino caprylic acid and its alkanol esters, the alkanol having from 1 to 4 carbon atoms, comprising treating a compound of the group consisting of 7-cyano-2,5-heptadienoic-l acid and the corresponding alkanol esters thereof with hydrogen in the presence of hydrogenation catalyst, the process being carried out in' two stages, in the first of which substantially only the two carbon to carbon double bonds are hydrogenated, palladium being used in the first stage and nickel in the second.

References Cited in the file of this patent UNITED STATES PATENTS 2,811,556 Shapiro Oct. 29, 1957 2,871,247

OTHER REFERENCES Nesmeyanov et al.: Izves. Acad. Nauk. S.S.S.R. 1955, 224-232, cited in Chemical Abstracts 50, 4849-4850 (1 956).

Seon et a1. Ian. 27, l1959 

14. A PROCESS FOR PREPARING A COMPOUND OF THE GROUP CONSISTING OF OMEGA-AMINO CAPRYLIC ACID AND ITS ALKANOL ESTERS,THE ALKANOL HAVING FROM 1 TO 4 CARBON ATOMS, COMPRISING TREATING A COMPOUND OF THE GROUP CONSISTING OF 7-CYANO-2,5-HEPTADIENOIC-1 ACID AND THE CORRESPONDING ALKANOL ESTERS THEREOF WITH HYDROGEN IN THE PRESENCE OF HYDROGENATION CATALYST, THE PROCESS BEING CARRIED OUT IN TWO STAGES, IN THE FIRST OF WHICH SUBSTANTIALLY ONLY THE TWO CARBON TO CARBON DOUBLE BONDS ARE HYDROGENATED, PALLADIUM BEING USED IN THE FIRST STAGE AND NICKEL IN THE SECOND. 